The conventional test procedures for high-pressure pumps which are provided to inject fuel into a combustion engine, what are referred to as “common-rail pumps”, start by switching on the test-oil supply. Immediately after that, the high-pressure pump is started, that is, rotational speed is applied to it. The high-pressure pump delivers the test oil into a high-pressure accumulator (common rail), whose internal pressure at the start (“pressure at rest”) is between 0 and 70 bar. This pressure at rest is a function of the design of the pressure regulating valves at the high-pressure accumulator.
After the setpoint speed is reached, the pressure control is started by supplying current to the pressure regulating valves that alter/adjust the outlet cross-section of the high-pressure accumulator in accordance with the setpoint pressure. Prior to a test-step change, which is associated with a modification of the speed of the high-pressure pump, the pressure regulating valves are de-energized for safety reasons in order to avoid an unintentional pressure rise in the high-pressure accumulator, or the pressure in the high-pressure accumulator is driven down to 0 bar. After the high-pressure pump has reached the next setpoint speed, the pressure in the high-pressure accumulator is set anew to the now desired (new) value, by suitable activation of the pressure regulating valves.
With the starting of test steps, a metering unit (MU) of the high-pressure pump is acted upon with the current provided in keeping with the test requirements. The MU regulates the feed quantity for the generation of high pressure in the low-pressure circuit of the high-pressure pump. The delivery quantity of the high-pressure pump is measured in each test step, and is the test criterion of the high-pressure pump.